Snap action electrical switch with contact flutter attenuation means



y 3, 1966 D. SCHWARZKOPF ETAL 3,249,710

SNAP ACTION ELECTRICAL SWITCH vWI'IH 1 CONTACT FLUTTER ATTENUATION MEANS Original Filed May 25, 1960 26 FIG. 2

FIG. 3

FIG. I

INVENTORS DANIEL SCHWARZKOPF JOSEPH J. ZEMKE 47m MKM AT'TO RNEYS United States Patent SNAP ACTION ELECTRICAL SWITCH WITH CON- This is a continuation of application Serial No. 31,176, filed May 23, 1960.

This invention relates to miniature, precision type snap switches. More particularly, this invention relates to a snap action switch including provisions for preventing fluttering and -arcin-g by increasing contact pressure up to and during the point of snap-over.

In general, the operation of the snap switches to which the invention pertains, is well known. Such switches usually employ a pair of stressed members which comprise an overcenter spring system having a snap-center position. Actuation of the switch moves one of the members beyond the snap-center position causing a sudden change in the direction of the forces exerted by the system, whereby a movable contact element is snapped from its initial position to a second position.

It can be shown that the force exerted upon the contact element by the spring system (which provides the contact pressure) diminishes towards zero as the spring system approaches its snap-center position. Normally, the actuator member is moved rapidly past the center position and the snap action of the switch is satisfactory. However, when the stressed members are moved very slowly towards the center position, the system may remain at the snap-center position for a relatively long period of time, under which condition there exists little or no pressure between the movable and stationary contacts. This produces problems of fluttering and contact arcing which are seriously detrimental to the proper operation of the switch. In circumstances wherein the switchis subjected to vibration or shock, these undesirable effects may also be noticed for similar reasons.

Accordingly, it is an object of this invention to avoid I V the above mentioned drawbacks.

Another object is to provide increased contact pressure up to and during the point of snap-over of a precision type snap-action switch.

These and other objects of the invention are accomplished by the provision of an auxiliary spring member cooperating with the movable contact and a stationary contact of the switch. The auxiliary spring member is .adapted to be deformed when the movable contact is touching the stationary contact to provide an additional force which urges the contacts together. The auxiliary springmember may be dimensioned so that it remains deformed until the movable contact is moved beyond the .snap-center of system.-

The manner in which the above objects are accomplished will be explained in greater detail below with reference to the following description and drawings, wherein:

FIG. 1 is a side elevation view in partial cross section of the invention with parts broken away;

FIG. 2 is a top plan view of the carrier spring and snap mechanism; and

FIG. 3 is an end view of FIG. 1 along line 3--3.

Referring to the drawings in particular, a switch housing 10 is made of insulating material and carries two pairs of upper and lower stationary switch contacts respectively numbered 12 and 14, connected to suitable terminal strips 16. A securing means 18 such as a rivet or the like anchors a contact carrying spring leaf 24, a snap spring mechanism 22 and a snap mechanism bracket 20 to housing 10. The snap spring 2 2 has an integral curved spring portion 23 which abuts against a notched portion in the bracket 20. Above the snap mechanism and operated thereby is a contact carrying spring leaf 24 having two elongated leg portions 28-. Mounted on the end of the carrier spring 24 away from the anchor point 18 are a pair of movable contact means including upper contacts 26 and downward extensions 27 which are located in axial alignment with the upper and lower stationary contacts 12 and 14, respectively. Also contained at 'thefree end of the carrier spring 24 are spring finger portions 30 and 32, each formed from portions of the carrier spring 24. Theupper finger 30 lies along the longitudinal center line of the carrier spring 24 and between the moving contacts 26. The lower finger portion 32 is formed from the end of the spring 24 into a U-shaped loop to engage the underside of the free end of the snap spring 22. A reciprocable actuating plunger 34 is positioned through an aperture in the switch housing 10 and operates against a cross web portion 2 5 of the snap spring 22 through a suitable rectangular aperture cut in the carrier spring 24.

Thus, by applying downward pressure on the plunger 64, the snap point of spring 22 occurs and the resulting force is transmitted to the lower spring finger 32 along the longitudinal center of spring 24. Since the legs 28 of the carrier spring 24 increase its torsional flexibility, the applied force is equalized between each of the contacts. Thus, any irregularity in the height or location of the contacts 12 and 14 will be compensated for, thereby permitting the use of standard manufacturing tolerances in the fabrication of the switch parts. It is important in switches of this type that contact separation and closure be simultaneous. The combination described will yield this result through a wide range of conditions.

By applying the snap mechanism switch operating force to the movable contact 26 through the resilient spring fingers 30 and 32, the force is applied in such a manner as to oppose the force resulting from the snap mechanism at the contacts, and permits the establishment of conditions under which contact forces do not decrease to zero at snap over, but'can be made to some higher value.

When the switch is in the position illustrated in FIG. 1, spring finger 30 is deformed due to the forces exerted by the snap-action mechanism and spring leaf 24. The deformed spring finger 30 pushing against leaf 24 urges movable contact 26 against stationary contact 12, thus increasing the contact pressure therebetween. When the switch is'actuated by the downward movement of actuator button 34, the force due to the snap-action mechanism decreases towards zero. However, since the switch is primarily responsive to the position of the snap-action mechanism (stressed members 22 and 23) which does not change until the point of snap-over, spring finger 30 continues to exert an additional force pushing contact 26 against contact 12. After the snap-action mechanism has passed beyond the point of snap-over, the position of the snap-action mechanism is sufiiciently altered so that spring finger 30 is no longer deformed and the force exerted Patented May a, 19.66

deformation of this spring finger. Since spring finger 32 is an extension of spring leaf 24, which is secured to the movable contact extension 27, the deformed spring finger 32 pulls extension 27 downwardly with an additional force against stationary contact 14. As in the case of spring finger 30, this increased contact pressure is maintained when the actuator is released up to and, if desired, slightly beyond the return snap center of the switch.

Those skilled in the art will readily appreciate that the same improved manner of operation of the invention could be obtained by spring members working in conjunction and as a part of the mounting for the stationary contacts instead of as in the present embodiment wherein the stationary contacts are fixed to the housing.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the invention principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

We claim: 9

1. For use with a snap action switch, including at least one stationary contact, a movable contact, a carrier member mounting said movable contact, means for mounting said stationary contact and said carrier member,

and a snap mechanism comprising at least two position responsive stressed members having a snap center, said stressed members being interconnected at one end and having a curved spring portion abutting against said mounting means, said stressed members biasing said carrier member with said movable contact toward said stationary contact when said stressed members are positioned on one side of said snap center, and biasing said carrier member away from said stationary contact when said stressed members are positioned on the other side of said snap center; an additional deformable spring finger integral with said carrier member and biased against said snap mechanism for urging said movable contact toward said stationary contact when said stressed members are positioned on said one side, said spring finger being deformed against said snap mechanism until said stressed members are moved beyond said snap center thereby maintaining positive contact pressure between said movable contact and said stationary contact until snap over.

2. A snap action switch, including first and second stationary contacts, a carrier blade, means for mounting said blade and said stationary contacts, a movable contact mounted on said blade, a snap mechanism including two position responsive stressed members having a snap center, said members being interconnected at one end and having a curved spring portion abutting against said mounting means to bias said carrier blade toward said first stationary contact when said members are positioned on one side of said snap center, and to bias said blade toward said second stationary contact when said members are positioned on the other side of said snap center, a first deformable spring finger integral with said carrier blade and biased against said snap mechanism, said first finger urging said blade toward said first stationary contact when said stressed members are positioned on said one side, and a second deformable spring finger integral with said carrier blade and biased oppositely against said snap mechanism from said first springrfinger, said second finger urging said blade toward said second stationary contact when said stressed members are positioned on said other side, one of said spring fingers being deformed against said snap mechanism when said stressed members are at said snap center, thereby maintaining positive contact pressure between said movable contact and said stationary contact until snap over.

3. A snap action switch according to claim 2, wherein said spring fingers extend from said carrier blade and said snap mechanism is positioned between said spring fingers, one of said spring fingers contacting the upper surface of said snap spring mechanism and the other spring finger contacting the under surface of said snap mechanism.

4. A snap action switch according to claim 3, wherein said one spring finger comprises a downwardly extending resilient member, and said other spring finger comprises a generally U-shaped resilient member.

5. A snap action switch according to claim 4, wherein said spring fingers are integrally formed with said carrier blade.

6. A snap action switch according to claim 2, wherein said carrier blade includes two resilient elongated legs interconnected at one end, said movable contact being mounted at said end, a second movable cont-act also mounted at said end, and third and fourth stationary contacts for engaging said second movable contact.

References Cited by the Examiner UNITED STATES PATENTS I 2,181,068 11/1939 Riche 2007 2,228,523 1/ 1941 Johnson. 2,418,068 3/ 1947 Cornelius 20067 2,500,476 3/ 1950 Von Stoeser 20067 2,519,334 8/1950 Arbogast 200-67 2,821,588 l/ 1958 Fisher 20067 KATHLEEN H. cLAEFY, Primary Examiner".

ROBERT K. SOHABFER, Examiner. 

1. FOR USE WITH A CAP SNAP ACTION SWITCH, INCLUDING AT LEAST ONE STATIONARY CONTACT, A MOVABLE CONTACT, A CARRIER MEMBER MOUNTING SAID MOVABLE CONTACT, MEANS FOR MOUNTING SAID STATIONARY CONTACT ADN SAID CARRIER MEMBER, AND A SNAP MECHANISM COMPRISING AT LEAST TWO POSITIONS RESPONSIVE STRESSED MEMBERS HAVING A SNAP CENTER, SAID STRESSED MEMBERS BEING INTECONNECTED AT ONE END AND HAVING A CURVED SPRING PORTION ABUTTING AGAINST SAID MOUNTING MEANS, SAID STRESSED MEMBERS BIASING SAID CARRIER MEMBER WITH SAID MOVABLE CONTACT TOWARD SAID STATIONARY CONTACT WHEN SAID STRESSED MEMBERS ARE POSITIONED ONE ONE SIDE OF SAID SNAP CENTER, AND BIASING SAID CARRIER MEMBER AWAY FROM SAID STATIONARY CONTACT WHEN SAID STRESSED MEMBERS ARE POSITIONED ON THE OTHER SIDE OF SAID SNAP CENTER; AND ADDITIONAL DEFORMABLE SPRING FINGER INTEGRAL WITH SAID CARRIER MEMBER AND BIASED AGAINST SAID SNAP MECHANISM FOR URGING SAID MOVABLE CONTACT TOWARD SAID STATIONARY CONTACT WHEN SAID STRESSD MEMBERS ARE POSITIONED ON SAID ONE SIDE, SAID SPRING FINGER BEING DEFORMED AGAINST SAID SNAP MECHANISM UNTIL SAID STRESSED MEMBERS ARE MOVED BEYOND SAID SNAP CENTER THEREBY MAINTAINING POSITIVE CONTACT PRESSURE BETWEEN SAID MOVABLE CONTACT AND SAID STATIONARY CONTACT UNTIL SNAP OVER. 